U.S. patent application number 12/394815 was filed with the patent office on 2009-06-25 for molten metal pressure pour furnace.
This patent application is currently assigned to HI T.E.Q., INC.. Invention is credited to Gordon F. KENNEDY, Mark G. MOHLER.
Application Number | 20090159231 12/394815 |
Document ID | / |
Family ID | 31999138 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090159231 |
Kind Code |
A1 |
KENNEDY; Gordon F. ; et
al. |
June 25, 2009 |
Molten Metal Pressure Pour Furnace
Abstract
An apparatus and process are provided for discharging a dose of
a molten metal from a pressure pour furnace. A heating chamber of
the furnace is used to keep the molten metal at a selected
temperature. A sealing port between the heating chamber and a
pressure chamber allows selectively filling of the pressure chamber
with molten metal from the heating chamber by inserting or removing
a sealing means from the sealing port. The sealing means inserted
in the sealing port also provides a means for preventing back flow
of the molten metal to the heating chamber when the pressure
chamber is pressurized. Differential pressure sensing of the
pressure of the molten metal in the pressure chamber and the
pressure of the pressurizing gas in the pressure chamber can
optionally be used to achieve an accurate measured discharge from
the pressure chamber as the level of molten metal decreases from
repeated discharges of doses from the furnace. The sealing plate in
which the sealing port is disposed and the sealing means
selectively inserted or removed from the sealing port can be used
as a metering valve between two molten metal containing components
such as a launder and a pressure chamber of a pressure pour
furnace.
Inventors: |
KENNEDY; Gordon F.;
(Sarasota, FL) ; MOHLER; Mark G.; (Moraine,
OH) |
Correspondence
Address: |
PHILIP O. POST;INDEL, INC.
PO BOX 157
RANCOCAS
NJ
08073
US
|
Assignee: |
HI T.E.Q., INC.
Columbus
OH
|
Family ID: |
31999138 |
Appl. No.: |
12/394815 |
Filed: |
February 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11862735 |
Sep 27, 2007 |
7497989 |
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12394815 |
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|
10382150 |
Mar 5, 2003 |
7279128 |
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11862735 |
|
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60413183 |
Sep 24, 2002 |
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60410408 |
Sep 13, 2002 |
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Current U.S.
Class: |
164/119 ;
222/590 |
Current CPC
Class: |
B22D 18/04 20130101 |
Class at
Publication: |
164/119 ;
222/590 |
International
Class: |
B22D 27/13 20060101
B22D027/13; B22D 37/00 20060101 B22D037/00 |
Claims
1. A method of discharging a dose of a molten metal from a pressure
pour furnace, the method comprising the steps of: venting a
pressure chamber of the furnace to atmospheric pressure; opening a
sealing port disposed in a wall between the pressure chamber and a
heating chamber of the furnace by removing a sealing element from
the sealing port to allow the flow of the molten metal from the
heating chamber through the sealing port to the pressure chamber;
closing the sealing port by inserting the sealing element into the
sealing port to prevent the flow of the molten metal from the
heating chamber through the sealing port to the pressure chamber;
substantially sealing the pressure chamber from atmospheric
pressure; providing a dosing tube through a dosing tube opening in
the pressure chamber, the dosing tube comprising a first and second
contiguous sections, the first section disposed exterior to the
pressure chamber and terminating in a dosing tube pour end, the
second section disposed interior to the pressure chamber and
terminating in a dosing tube supply end; extending the dosing tube
pour end away from the pressure chamber; and injecting a gas into
the volume above the surface of the molten metal in the pressure
chamber to force an at least one dose of the molten metal through
the dosing tube and out of the dosing tube pour end.
2. The method of claim 1 further comprising the step of injecting
the gas above the surface of the molten metal in the pressure
chamber to a ready level prior to the step of injecting the gas
into the volume above the surface of the molten metal in the
pressure chamber to force an at least one dose of molten metal
through the dosing tube and out of the dosing tube pour end.
3. The method of claim 1 wherein the steps of opening or closing
the sealing port further comprises raising or lowering a sealing
tube having a first and second opposing ends, the sealing element
attached to the first end of the sealing tube, and the second end
of the sealing tube protruding through a sealing tube opening in
the wall of the pressure chamber, the sealing tube opening
pressure-sealed by a bellows having a first and second opposing
ends, the first end of the bellows attached to the wall of the
pressure chamber around the sealing tube opening and the send end
of the bellows attached around the sealing tube external to the
pressure chamber.
4. The method of claim 1 further comprising the steps of forming
the sealing port from the combination of a cylindrically-shaped
elbow passage and a conically-shaped passage, and orienting the
elbow passage so that the molten metal flows through the elbow
passage in a substantially horizontal path out of the heating
chamber and a substantially vertical path into the conically-shaped
passage in the pressure chamber when the sealing element is removed
from the conically-shaped passage.
5. The method of claim 1 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises the steps of
extending a first partial section of the first section of the
dosing tube from the remainder of the first section of the dosing
tube, the first partial section of the first section of the dosing
tube terminating in the dosing tube pour end, and providing a
bellows sealing element around the first partial section and the
remainder of the first section of the dosing tube.
6. The method of claim 1 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises extending
the first and second sections of the dosing tube, and providing a
bellows sealing element around the first section and the dosing
tube opening in the pressure chamber.
7. A method of providing a dose of a molten metal, the method
comprising the steps of: producing the molten metal by heating a
metal charge in an at least one metal melting furnace; supplying
the molten metal to a heating chamber of an at least one molten
metal pressure pour furnace by a launder; venting a pressure
chamber of the at least one molten metal pressure pour furnace to
atmospheric pressure; opening a sealing port disposed in a wall
between the pressure chamber and the heating chamber of the at
least one molten metal pressure pour furnace by removing a sealing
element from the sealing port to allow the flow of the molten metal
from the heating chamber through the sealing port to the pressure
chamber; closing the sealing port by inserting a sealing element
into the sealing port to prevent the flow of the molten metal from
the heating chamber through the sealing port to the pressure
chamber; substantially sealing the pressure chamber from
atmospheric pressure; providing a dosing tube through a dosing tube
opening in the pressure chamber, the dosing tube comprising a first
and second contiguous sections, the first section disposed exterior
to the pressure chamber and terminating in a dosing tube pour end,
the second section disposed interior to the pressure chamber and
terminating in a dosing tube supply end; extending the dosing tube
pour end away from the pressure chamber; and injecting a gas into
the volume above the surface of the molten metal in the pressure
chamber to force an at least one dose of the molten metal through
the dosing tube and out of the dosing tube pour end.
8. The method of claim 7 further comprising the steps of forming
the sealing port from the combination of a cylindrically-shaped
elbow passage and a conically-shaped passage and orienting the
elbow passage so that the molten metal flows through the elbow
passage in a substantially horizontal path out of the heating
chamber and a substantially vertical path into the conically-shaped
passage into the pressure chamber when the sealing element is
removed from the conically-shaped passage.
9. The method of claim 7 further comprising the step of injecting
the gas above the surface of the molten metal in the pressure
chamber to a ready level prior to the step of injecting the gas
into the volume above the surface of the molten metal in the
pressure chamber to force an at least one dose of molten metal
through the dosing tube and out of the dosing tube pour end.
10. The method of claim 7 wherein the steps of opening or closing
the sealing port further comprises raising or lowering a sealing
tube having a first and second opposing ends, the sealing element
attached to the first end of the sealing tube, and the second end
of the sealing tube protruding through a sealing tube opening in
the wall of the pressure chamber, the sealing tube opening
pressure-sealed with a bellows having first and second opposing
ends, the first end of the bellows attached to the wall of the
pressure chamber around the sealing tube opening and the second end
of the bellows attached around the sealing tube exterior to the
pressure chamber.
11. The method of claim 7 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises the steps of
extending a first partial section of the first section of the
dosing tube from the remainder of the first section of the dosing
tube, the first partial section of the first section of the dosing
tube terminating in the dosing tube pour end, and providing a
bellows sealing element around the first partial section and the
remainder of the first section of the dosing tube.
12. The method of claim 7 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises extending
the first and second sections of the dosing tube, and providing a
bellows sealing element around the first section and the dosing
tube opening in the pressure chamber.
13. A method of discharging a dose of molten metal from a pressure
pour furnace, the method comprising the steps of: venting a
pressure chamber of the furnace to atmospheric pressure; opening a
sealing port disposed in a wall between the pressure chamber and a
heating chamber of the furnace by removing the end of a sealing
tube from an opening in the sealing port to allow the flow of the
molten metal from the heating chamber through the sealing port to
the pressure chamber, the opening in the sealing port disposed in
the pressure chamber; energizing a sealing tube close actuator to
initiate movement of the end of the sealing tube towards the
opening in the sealing port; seating the end of the sealing tube in
the opening in the sealing port to terminate flow of the molten
metal from the heating chamber to the pressure chamber;
substantially sealing the pressure chamber from atmospheric
pressure; providing a dosing tube through a dosing tube opening in
the pressure chamber, the dosing tube comprising a first and second
contiguous sections, the first section disposed exterior to the
pressure chamber and terminating in a dosing tube pour end, the
second section disposed interior to the pressure chamber and
terminating in a dosing tube supply end; injecting a pour gas into
the volume above the surface of the molten metal in the pressure
chamber to force the molten metal into the supply end of the dosing
tube; sensing when the level of molten metal in the dosing tube has
reached a ready level to regulate the pressure of the gas to
maintain the level of molten metal in the dosing tube at the ready
level; indexing the sprue of a mold adjacent to the dosing tube
pour end; extending the dosing tube pour end to the sprue of the
indexed mold; injecting the pour gas into the volume above the
surface of the molten metal in the pressure chamber at a mold fill
profile gas injection rate to force the molten metal out of the
dosing tube pour end and into the sprue of the indexed mold to fill
the interior volume of the mold; adjusting the gas injection rate
to return the level of molten metal in the dosing tube to the ready
level; and retracting the dosing tube pour end from the sprue of
the indexed mold.
14. The method of claim 13 further comprising the steps of forming
the sealing port from the combination of a cylindrically-shaped
elbow passage and a conically-shaped passage, and orienting the
elbow passage so that the molten metal flows through the elbow
passage in a substantially horizontal path out of the heating
chamber and a substantially vertical path into the conically-shaped
passage into the pressure chamber when the sealing element is
removed from the conically-shaped passage.
15. The method of claim 13 further comprising the step of sensing
the back force loading on the sealing tube actuator to detect
blockage in the opening of the sealing port as the end of the
sealing tube moves toward the sealing port.
16. The method of claim 13 wherein the step of sensing when the
level of molten metal in the dosing tube has reached a ready level
further comprises the step of injecting a melt pressure sensing gas
into a melt pressure sensing tube having an end immersed in the
molten metal in the pressure chamber to sense a melt pressure
sensing gas bubble release from the immersed end of the melt
pressure sensing tube corresponding to the level of molten metal in
the dosing tube having reached the ready level.
17. The method of claim 13 further comprising the step of passing a
stream of pressurized air across the dosing tube pour end to
dislodge molten metal after retracting the dosing tube pour end
opening from the sprue in the mold.
18. The method of claim 13 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises the steps of
extending a first partial section of the first section of the
dosing tube from the remainder of the first section of the dosing
tube, the first partial section of the first section of the dosing
tube terminating in the dosing tube pour end, and providing a
bellows sealing element around the first partial section and the
remainder of the first section of the dosing tube.
19. The method of claim 13 wherein the step of extending the dosing
tube pour end away from the pressure chamber comprises extending
the first and second sections of the dosing tube, and providing a
bellows sealing element around the first section and the dosing
tube opening in the pressure chamber.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of application Ser. No.
11/862,735, filed Sep. 27, 2007, which is a divisional application
of application Ser. No. 10/382,150, filed Mar. 5, 2003, now U.S.
Pat. No. 7,279,128, which application claims the benefit of U.S.
Provisional Application No. 60/410,408, filed Sep. 13, 2002, and
U.S. Provisional Application No. 60/413,183 filed Sep. 24, 2002,
all of which applications are incorporated herein by reference in
their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates generally to molten metal
pressure pour furnaces, and in particular, to such furnaces wherein
a repeatedly precise dose of molten metal is discharged from the
furnace. The present invention further relates to a molten metal
flow valve that can be used with molten metal pressure pour
furnaces.
BACKGROUND OF THE INVENTION
[0003] Pressure pour or dosing furnaces can be used to discharge
repeated and measured doses of a molten metal from the furnace for
filling a continuous line of molds. The opening to the sprue of a
mold is brought in contact with the outlet of the furnace and a gas
is used to exert pressure on the molten metal in the furnace, which
forces a measured dose of the melt into the sprue, through the
gating system and into the mold cavities. Molds can be sequentially
filled in the process.
[0004] U.S. Pat. No. 4,220,319 to Rohmann discloses a single
chamber pressure pour furnace. A metered discharge from the furnace
is accomplished by differential pressure sensing of air in the
pressurized chamber. The pressure at which molten metal in the
chamber rises to the end of the outlet tube prior to each discharge
is sensed. This pressure reading is used as the baseline pressure
at the start of a pour. The pour is terminated by release of
pressure in the chamber when the chamber pressure reaches a
selected value.
[0005] U.S. Pat. No. 5,477,907 to Meyer et al discloses a pressure
chamber that is isolated from a heating chamber by a wall with an
opening through it. A backloading air regulator is used to account
for the pressure increase in the pressure chamber that is required
for the molten metal to rise to the end of the outlet tube before
the timed period of discharge is started. Further backflow of
molten metal into the heating chamber is allowed through the
opening in the wall when the pressure chamber is pressurized.
[0006] U.S. Pat. No. 5,913,358 to Chadwick discloses the use of a
non-return valve in the wall between the pressure chamber and
heating chamber to prevent the backflow of molten metal when the
pressure chamber is pressurized. The non-return valve is disclosed
typically as a ball and socket valve that acts automatically to
prevent reverse flow. A potential disadvantage of this arrangement
is that the molten metal, or particulate in the melt, could lodge
the ball in a position that permanently blocks flow of the molten
metal from the heating chamber to the pressure chamber as required
to replenish the supply of melt in the chamber.
[0007] U.S. Pat. No. 5,590,681 to Schaefer et al. discloses a plug
valve assembly integral with upstream and down stream launder
sections. The upstream launder section is connected to a low
pressure casting furnace, and the upstream launder section is
connected to a supply of molten metal. Flow between the supply and
the low pressure casting furnace is controlled by the plug valve
assembly.
[0008] One object of the present invention is to provide a pressure
pour furnace wherein the pressure differential between the molten
metal at a selected level in the pressure chamber and the
pressurized gas used to perform a pressure pour in the pressure
chamber is used to provide a repeatedly precise measured discharge
of melt from the furnace. Another object of the present invention
is to control the flow of molten metal to the pressure chamber of a
pressure pour furnace with a compact metering valve arrangement
that will also provide an efficient method of blocking backflow of
the molten metal from the pressure chamber into the heating
chamber, or metal supply chamber, when the pressure chamber is
pressurized.
BRIEF SUMMARY OF THE INVENTION
[0009] In one aspect, the present invention is an apparatus for,
and method of, discharging a dose of molten metal, or melt, from a
furnace comprising a receiving chamber, heating chamber and
pressure chamber. Molten metal is supplied to the receiving
chamber; maintained at a desired temperature in the heating
chamber; and discharged from the pressure chamber. A sealing plate
having a sealing port in it is disposed between the heating chamber
and the pressure chamber to control the flow of melt from the
heating chamber to the pressure chamber by the insertion or removal
of a sealing means in the sealing port. Insertion of the sealing
means in the sealing port also prevents the back flow of melt from
the pressure chamber to the heating chamber when the pressure
chamber is pressurized. A gas injected into the pressure chamber is
used to force the melt from an outlet dosing tube in the pressure
chamber and into a suitable container. The dosing tube may be
extend from the pressure chamber for connection with a mold for
filing and retracted into the pressure chamber after the mold is
filled. In one example of the invention, the means for blocking the
back flow of melt from the pressure chamber to the heating chamber
is a sealing means that substantially blocks the back flow of melt
through the sealing port in a composite high thermal conductivity
ceramic sealing plate and port.
[0010] In another aspect, the present invention is a system for
delivering doses of molten metal from one or more molten metal
pressure pour furnaces when the molten metal is supplied from one
or more metal melting furnaces by a launder network. One or more
heat treatment processes may be performed on the molten metal
before being delivered to the metal pressure pour furnaces by the
launder network.
[0011] In another aspect, the present invention is a metering valve
that can be formed from a sealing plate that prevents the flow of
molten metal between two adjoining molten metal containing
components such as a launder and the pressure chamber of a pressure
pour furnace. The sealing plate has a sealing port disposed in it
to allow the flow of molten metal when a sealing means is not
inserted in the sealing port and to prevent the flow of molten
metal when the sealing means is inserted in the sealing port.
[0012] These aspects of the invention are further set forth in this
specification, and other aspects of the invention are as set forth
in this specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For the purpose of illustrating the invention, there is
shown in the drawings a form that is presently preferred; it being
understood, however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
[0014] FIG. 1 is a cross sectional view of one example of the
molten metal pressure pour furnace of the present invention.
[0015] FIG. 2 is a top view of one example of a pressure chamber
used in a molten metal pressure pour furnace of the present
invention.
[0016] FIG. 3 is a cross sectional view of the pressure chamber
illustrated in FIG. 2 at line A-A.
[0017] FIG. 4 is a cross sectional view of the pressure chamber
illustrated in FIG. 2 at line B-B.
[0018] FIG. 5 is a partial cross sectional view of the pressure
chamber illustrated in FIG. 4 with the additional feature of a
double bellows arrangement around the dosing tube.
[0019] FIG. 6(a) illustrates one example of a metering valve used
to control flow of a molten metal between adjoining molten metal
containing components.
[0020] FIG. 6(b) and FIG. 6(c) illustrate one example of a dosing
tube and dosing tube assembly used in the pressure chamber of a
molten metal pressure pour furnace of the present invention.
[0021] FIG. 7 diagrammatically illustrates one example of an
integrated arrangement of molten metal supply sources, molten metal
heat treatment vessels and the molten metal pressure pour furnaces
of the present invention.
[0022] FIG. 8(a) through FIG. 8(h) is a flowchart of an example of
a control process that can be used for the molten metal pour
furnace of the present invention.
[0023] FIG. 9(a) illustrates a metering valve of the present
invention that is used to regulate the flow of a molten metal into
a low pressure pour furnace.
[0024] FIG. 9(b) diagrammatically illustrates an integrated
arrangement of molten metal supply sources, molten metal heat
treatment vessels and a plurality of the metering valves of the
present invention that are used to regulate the flow of a molten
metal into a plurality of low pressure furnaces.
[0025] FIG. 10(a) illustrates a double metering valve arrangement
of the present invention that is used to regulate the flow of a
molten metal into a low pressure pour furnace.
[0026] FIG. 10(b) diagrammatically illustrates an integrated
arrangement of molten metal supply sources, molten metal heat
treatment vessels and a plurality of the double metering valve
arrangements of the present invention that are used to regulate the
flow of a molten metal into a plurality of low pressure
furnaces.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Referring now to the drawings, wherein like numerals
indicate like elements, there is shown in the drawings, one example
of the molten metal pressure pour furnace 10 of the present
invention. The furnace comprises a receiving chamber 12, heating
chamber 14 and pressure chamber 16. The furnace's exterior support
structure 18 is formed from a suitable material such as a mild
steel, and may be lined with a suitable refractory 20 such as
multicomponent refractory materials as known in the art. As
explained in further detail below: receiving chamber 12 is supplied
with molten metal, or melt, from a suitable source; heating chamber
14 maintains the melt at a suitable temperature; and pressure
chamber 16 discharges a measured dose of melt from the furnace.
When furnace 10 provides molten metal to a continuous line of
molds, the pressure chamber usually holds a sufficient quantity of
melt for filling multiple molds in succession. When required the
molten metal in the pressure chamber is replenished with melt from
the heating chamber. Molten metal load line 11 (shown as a dashed
line) in FIG. 1 illustrates a typical fully loaded furnace.
[0028] Receiving chamber 12 can be supplied with molten metal, such
as, but not limited to, a liquid aluminum composition, by a
suitable pumping system or launder. In one example of the
invention, the supply of melt is provided by a launder delivery
system connected to a melt and metal treatment system wherein the
launder delivery system maintains a substantially constant level of
molten metal in the receiving chamber. For example, aluminum ingots
and scrap may be melted in a stack furnace to produce liquid
aluminum that is collected in a holding furnace. The liquid
aluminum may be further treated to remove hydrogen gas, oxides,
impurities and other active metals in a filtering vessel that is
fed from the holding furnace. Either a gravity feed or pumped
launder delivery system may be connected between the holding
furnace or filtering vessel and receiving chamber 12. A means for
sensing the level of molten metal in the receiving chamber or
launder delivery system, such as a laser sensing system or
mechanical float switch, can be used to sense the level of melt for
control of the flow of molten metal from the holding furnace or
filtering vessel to the receiving chamber so that a substantially
constant height of melt is continuously maintained in the receiving
chamber. Receiving chamber 12 may also include means for degassing
the melt in the chamber, such as a carbon diffusion lance, floor
purge plugs or a rotary dispersion lance top, as used to inject
chlorine gas, nitrogen or argon into liquid aluminum. Further the
launder delivery system may be arranged so that a single supply of
melt is distributed to a plurality of pressure pour furnaces.
[0029] Heating chamber 14 is partially separated from receiving
chamber 12 by furnace arch 23 which is formed from a suitable
refractory composition. Heating chamber 14 includes suitable means
for heating melt in the chamber, such as electric heating elements
20, or fossil fuel fired burners. Fossil fuel fired burners are
less advantageous in that combustion gas byproducts may contaminant
melt in the heating chamber. Suitable resistive electric heating
elements are preferably of a high watt density type such as those
formed from a silicon carbide composition. Furnace arch 23 serves
as a means for retaining heat and a protective atmosphere within
the heating chamber, and prevents any melt perturbations in the
receiving chamber from propagating into the heating chamber.
Normally the heights of the melt in the receiving and heating
chambers are the same. Heating elements 20 are a part of a furnace
heating system that maintains a pre-selected temperature of the
molten metal in the heating chamber. One or more means for sensing
temperature of the melt in the furnace, such as immersed
thermocouple 21 is used as an input to a processing means, such as
a programmable logic controller (PLC). The processing means
provides an output signal to the means for heating the molten metal
in the heating chamber. For example, if electric resistive heating
elements are used, the output signal may be used to control the
switching of silicon controlled rectifiers (SCRs) in an SCR heater
controller. Temperature sensing may include differential
temperature sensing of the molten metal in the receiving and
heating chambers. Preferably heating chamber 14 includes a
non-reactive gas purging system wherein a gas, such as nitrogen, is
used to purge the air above the surface of the molten metal in the
heating chamber to minimize the formation of oxide on the surface,
and minimize the diffusion of contaminants into the molten metal,
such as hydrogen gas in liquid aluminum. Optionally porous floor
plugs may also be provided in the heating chamber to purge
contaminants in the molten metal, such as hydrogen gas in aluminum,
by flowing a non-reactive gas, such as nitrogen or argon, through
the melt.
[0030] Pressure chamber 16 is separated from heating chamber 14 by
a composite sealing plate and port 22 as best illustrated in FIG.
6(a). In one non-limiting example of the invention, the composite
sealing plate and port is integrally cast from a high thermal
conductivity ceramic such as a nitrite bonded silicon carbide or
other ceramic composition. Use of such composition is desireable
for retaining adequate heat content in the melt in the pressure
chamber. Alternatively, the sealing port may be separately
fabricated and attached to the sealing plate. The port provides a
means for flow of melt from the heating chamber to the pressure
chamber. A sealing means for insertion into the sealing port
substantially blocks the back flow of molten metal from the
pressure chamber to the heating chamber through the port when the
pressure chamber is pressurized, as well as blocking flow of the
molten metal from the heating chamber to the pressure chamber. The
top of pressure chamber 16 is substantially sealed from the ambient
environment by a suitable wall or lid 26 and seals around
penetrating openings for elements as further described below. The
lid may be fabricated from a mild steel plate that is suitably
fastened to the pressure chamber.
[0031] The means for substantially blocking the back flow of molten
metal from the pressure chamber to the heating chamber comprises a
sealing means inserted into the sealing port. In this non-limiting
example of the invention, the sealing means comprises sealing
element 30a at one end of sealing tube 30, wherein sealing element
30a is generally hemispherical in shape and seats into a generally
conically-shaped sealing port to substantially block the back flow
of molten metal from the pressure chamber when the pressure chamber
is pressurized as further described below. The sealing tube and
element may be cast from a heat-resistant and wear-resistant
material, such as a nitrite bonded silicon carbide or other ceramic
composition.
[0032] As shown in the non-limiting example of the metering valve
of the present invention in FIG. 6(a), sealing port 22 comprises a
substantially conically-shaped section at one end of the port with
its longitudinal axis generally vertically aligned. The smaller
diameter end of the conically-shaped section is connected to a
substantially cylindrically-shaped section that is elbow-shaped so
that the substantially vertical flow of the melt through the
conically-shaped section of an open sealing port is redirected to a
substantially horizontal flow at the other end of the sealing port.
Conversely flow in the opposite direction first flows through the
elbow-shaped section and then through the conically-shaped section
of the sealing port. The sealing port is integrally attached to
sealing plate 25 in this particular example of the invention.
Sealing plate 25 serves as the barrier between two adjoining molten
metal containing elements.
[0033] Sealing port 22 and the sealing means for allowing or
preventing flow of the melt through the port comprise a metering
valve that generally controls the flow of melt to adjoining molten
metal containing elements. In this particular application, the
adjoining molten metal containing elements are the heating chamber
and the pressure chamber of a molten metal pressure pour
furnace.
[0034] Dosing tube 32 extends obliquely through wall or lid 26 into
the molten metal in the pressure chamber and serves as a means for
discharging a metered amount of melt from the pressure chamber. In
other examples of the invention the orientation of the dosing tube
relative to the top wall of the furnace may be different. As shown
in FIG. 3, dosing tube sealing bellows 34 surrounds the external
end of the dosing tube to provide a pressurized seal around the
opening in lid 26 through which the dosing tube penetrates. Use of
the bellows allows the pressure seal to be maintained as the dosing
tube is extended out of or retracted into the pressure chamber as
further described below.
[0035] FIG. 6(b) and FIG. 6(c) illustrate another example of the
dosing tube 32 and dosing tube assembly, respectively, of the
present invention. In this arrangement, three powered cylinders 33
(one not visible in the drawing) are used to extend and retract
dosing tube 32. Bellows 34 extend and retract with the dosing tube
to retain the pressurized seal around the dosing tube opening in
the wall of the pressure chamber. As further explained below
pressure plate 35 makes contact with the surface of a mold when the
dosing tube is extended. External end 32b of dosing tube 32 inserts
into the sprue of a mold when the dosing tube is extended.
[0036] Immersion tube heater 36 can be optionally provided to heat
melt in the pressure chamber if necessary to compensate for the
loss of heat from the melt in the pressure chamber. The auxiliary
heater may comprise a resistive silicon carbide heating element
disposed within a silicon nitrite tube that penetrates through lid
26 into the molten metal. A thermocouple within the tube can be
used to protect against overheating of the heating element.
Immersion temperature sensing device 37, such as a high thermal
conductivity silicon nitride thermocouple, is used as a sensor for
regulating the output of heater 36.
[0037] As best seen in FIG. 4, means for pressurizing the molten
metal in the pressure chamber is provided by injecting a gas (such
as dry air, argon or nitrogen) from a suitable supply 41, under
pressure, through gas port 38 located above the surface level of
the melt. A means for sensing the dynamic pressure on the molten
metal at a pre-selected height in the pressure chamber can be
provided by melt pressure sensing tube 40 and melt pressure sensor
42. One non-limiting method of sensing the melt pressure is to
bubble a non-reacting gas, such as nitrogen or argon, through the
tube at a pressure sufficient to prevent the melt from rising in
the melt pressure sensing tube and release a bubble at a
predetermined rate. A means for sensing the gas pressure of the gas
injected into the dosing chamber can be provided by gas pressure
sensing tube 44 and gas pressure sensor 46. Gas exhaust port 43 is
provided for controlled release of gas from the pressure chamber to
ambient air during the pour process or to depressurize the
chamber.
[0038] In one non-limiting method of operation, the pressure
chamber is substantially filled with melt from the heating chamber
to a height equal to the height of the melt in the heating chamber
by raising sealing tube 30 with a suitable actuator so that sealing
element 30a unseats from the sealing port to allow the flow of melt
from the heating chamber to the pressure chamber. Sealing tube
bellows 29 provides a pressurized seal around the opening through
which the sealing tube penetrates into the pressure chamber and
allows maintaining the seal as the sealing tube is raised or
lowered. After filling the pressure chamber, sealing tube 30 is
lowered so that sealing element 30a seats in the sealing port to
substantially block the back flow of melt into the heating chamber
as illustrated in FIG. 3. Optionally a heating element may be
provided in sealing element 30a to melt any molten metal that may
freeze in the sealing tube.
[0039] In some examples of the invention, gas is initially injected
into the pressure chamber to force melt in the chamber up the
dosing tube to approximately the external end of the riser tube.
This level of melt, which is referred to as the "ready level" is
used as a reference point for the start of every pour from the
pressure chamber. The ready level for a particular application may
be any height of melt in the dosing tube that is suitable for the
process. A means for sensing the presence of the melt at the
external end of the riser tube is provided. In one example of the
invention, the means comprise a pair of low voltage electrically
conducting probes 48 that form a normally open circuit when they
are not immersed in molten metal, and a closed circuit when they
are immersed in molten metal to indicate that the melt is at the
external end of the riser tube. A means is provided to move the
probes out of the opening of the riser tube. In this example, the
means comprise pivot arm 50, which is shown in the lowered and
raised (dashed lines) positions in FIG. 3. In alternate examples of
the invention a laser sensor may be used as the means for sensing
the presence of the melt at the external end of the riser tube.
[0040] Once the melt is raised to the external end of the dosing
(riser) tube (or other melt ready level), the opening of a
container, such as the opening in a mold sprue, is brought into the
vicinity of the external end of the riser tube, with the center of
the sprue opening approximately aligned with the center of the
opening in the riser tube. Dosing tube 32 is extended out of the
pressure chamber by means of a suitable actuator so that a
substantially pressurized seal is achieved between the end of the
riser tube and the opening in the mold sprue. Dosing tube sealing
bellows 34 expands to maintain the pressure seal around the opening
through which the dosing tube penetrates when the tube is in its
extended position. In some examples of the invention, a double
dosing tube bellows arrangement can be used as illustrated in FIG.
5. First dosing tube bellows 34a provides a pressurized seal around
the dosing tube opening in lid 26. Suitable actuators 90a and 90b,
preferably hydraulic cylinders due to the proximity to molten
metal, are used to extend or retract the dosing tube while first
dosing tube bellows 34a expands or contracts to maintain the seal.
Other types of actuators, such as hydraulically or electrically
driven actuators, may also be used. Second dosing tube bellows 34b
compresses as the end of the dosing tube seals around the opening
in the mold sprue to absorb any excess pressure exerted by the
mating mold surface.
[0041] A requisite amount of gas is injected into the pressure
chamber to discharge a measured dose of melt into the mold. The
volume and time rate of gas injection can initially be established
by an algorithm used by the processing means. After pressure
pouring the desired amount of molten metal into the mold, the riser
tube is retracted into the pressure chamber by means of a suitable
actuator. The molds are indexed by moving the filled mold and
placing an empty mold in its place. Between mold transitions,
probes 48 can be repositioned into the end of the dosing tube to
pressurize the pressure chamber to the level required to bring the
melt back up to the end of the dosing tube. The empty mold is then
filled by the process as described above for the previous mold.
[0042] Typically a filled pressure chamber can be used to fill a
number of molds, after which the level of melt in the pressure
furnace drops to a level that requires replenishment of the melt in
the pressure chamber from the heating chamber. One non-limiting
method of level sensing of the melt in the chamber can be
accomplished as a function of the applied gas pressure in the
chamber since increasing applied gas pressure is proportional to
the level of melt in the chamber. When replenishment is required,
sealing tube 30 is raised to allow a refill of the pressure
chamber. Gas exhaust port 43 is normally open when melt flows from
the heating chamber to the pressure chamber through the sealing
port during a refill. In alternative examples of the example,
vacuum pump 92 can be used to draw a vacuum on the pressure chamber
to increase the refill flow rate through the sealing port. This is
of particular advantage when a slower refill rate will not support
a fast indexing speed of molds. In other examples of the invention,
a gas may be injected under pressure into the volume above the melt
in heating chamber 14 to increase the refill flow rate through the
sealing port. If the heating chamber includes the optional
non-reactive gas purging system as described above, the purging
system may include means for gas pressurizing the melt in the
heating chamber. Pressurization of the melt in the heating chamber
for increased refill flow rate may optionally be combined with
vacuum draw on the pressure chamber. When the melt in heating
chamber 14 is under pressure, furnace arch 23 seals the gas volume
in the heating chamber from ambient air pressure. In alternate
examples of the invention, means may be provided for sealing
receiving chamber from ambient air pressure when melt in the
heating and/or receiving chamber is pressurized with a gas.
[0043] Use of the differential pressure method in some examples of
the invention enables accurate control of the measured dose from
the riser tube as the quantity of melt in the pressure chamber
reduces and the magnitude of applied pressure must increase. The
algorithm for pressure control may be adaptively adjusted for
future pours into the same type of mold by feedback of the sensed
differential pressure during the previous pour.
[0044] FIG. 8(a) through FIG. 8(h) illustrate one non-limiting
example of a process control flowchart routine that can be used to
discharge molten metal from a pressure pour furnace of the present
invention. The process control routine can be programmed by one
skilled in the art for execution by a suitable processor and
supporting computer hardware and software, and input and output
control devices. Starting on FIG. 8(a), with pressure chamber 16
vented to atmosphere, sealing port 22 open, and the pressure
chamber filled with melt, subroutine 102 is executed to energize
the sealing tube close actuator. The sealing tube close actuator
may be any suitable drive device for inserting sealing element 30a
into the sealing port. In this particular example of the invention,
the sealing tube actuator is pneumatically driven cylinder 27.
While the sealing element is moving to a seated position in the
sealing port, subroutine 104 is executed to sense whether there is
a blockage in the sealing port that prevents the sealing element
from properly seating in the sealing port. Blockage can be sensed
by back force loading (in this example, back air pressure) on the
sealing tube actuator. If a blockage is sensed, subroutine 106
activates a back pressure stop alarm that can be arranged to stop
the process operation and alert an operator to the abnormal
condition for correction of the abnormal condition. The sealing
element continues to move into the sealing port until subroutine
108 senses that the sealing port closed limit switch has been
activated. The sealing port closed limit switch may be a mechanical
limit switch mounted on the sealing tube assembly external to the
pressure chamber. The sealing port closed limit switch changes
state when the sealing element has completed full travel into the
sealing port and the de-energize sealing tube close actuator
subroutine 110 is executed to stop the actuator. At this time,
subroutine 112 may be executed to make a check of all systems
alarms, such as a low temperature alarm for melt in the pressure
chamber. If any alarm flag is in the alarmed state, then subroutine
114 activates a safety stop switch and subroutine 118 provides an
appropriate alarm indication to the operator. After appropriate
operator action, subroutine 120 clears the alarm, and the operator
de-activates the safety stop switch so that subroutine 121 can
return to the main process routine. If the alarm status is clear,
then subroutine 122 is executed to seal the pressure chamber from
atmospheric pressure. This can be accomplished by closing gas
exhaust port 43 and injecting gas into the pressure chamber from
gas supply 41
[0045] Gas is injected into the pressure chamber until the melt is
raised in dosing tube 32 to a level that is designated as the
"ready level". Alternative, and possibly a combination of, methods
may be used to sense the melt reaching the ready level. As
illustrated in FIG. 8(c) one method is by laser sensing of the
height of the melt in the dosing tube. The laser source is mounted
external to the pressure chamber and the laser beam is aimed at the
opening of the dosing tube. Subroutine 126 executes repeated
measurements of the laser beams "bounce back" time off of the
surface of the melt in the tube to determine the height of the melt
in the dosing tube. When the height reaches the designated ready
level, subroutine 132 holds the gas pressure at the melt ready
level. Alternatively, or in combination with laser sensing,
subroutine 128 can execute a "bubble tube" ready level sensing.
Bubble tube ready level sensing involves slowly injecting a gas
down melt pressure sensing tube 40 until melt pressure sensor 42
senses a slow pulse rate (e.g., approximately one pulse per second)
air supply, which indicates a slow bubble release of the gas into
the melt at the end of the sensing tube 40 immersed in the melt.
The pressure at that point in the melt is calibrated to the bubble
release rate, and the ready level of melt in the dosing tube can be
calculated in subroutine 128 from this pressure, the geometry of
the pressure vessel and the volume of melt discharged in each dose
of melt from the furnace. When the bubble tube ready level sensing
rate indicates the designated ready level, subroutine 132 holds the
gas pressure at the melt ready level. Alternative to the laser
sensing method is wire probe sensing of the ready level. For this
method subroutine 130 moves conducting probes 48 into the external
end of the dosing tube so that the tips of the two unconnected
probes are at the melt ready level. When melt rises up to the tips
of the two probes, the melt completes an electrical circuit that
outputs a signal indicating that the ready level has been reached.
At this point subroutine 132 holds the gas pressure at the melt
ready level.
[0046] With melt held at the ready level in the pressure chamber,
subroutine 133 is executed to sense whether a mold has been indexed
for filing by the mold line machinery. When subroutine 133 receives
a signal from the mold line machinery that a mold has been indexed
for filing, subroutine 134 energizes the dosing tube extend
actuator. The dosing tube extend actuator may be any suitable drive
device for extending the dosing tube for mating with the sprue of a
mold. In the example of the invention shown in FIG. 6(c), the
sealing tube actuator is three pneumatically driven cylinders 33.
The dosing tube continues to extend toward the surface of the
indexed mold until subroutine 136 senses that the end of the dosing
tube has made contact with the mold to ensure a sufficient seal
between the end of the dosing tube and the sprue of the mold so
that there is no leakage of melt from the connection when melt is
injected into the sprue of the mold. Pressure sensing can be
accomplished by utilizing a pressure load sensor behind pressure
plate 35 in the non-limiting example of the invention shown in FIG.
6(c). When the sensed pressure reaches a preset level for
sufficient sealing, de-energize dosing tube extend actuator
subroutine 138 is executed to stop the actuator.
[0047] Subroutine 140 injects more gas into the pressure chamber in
accordance with a predetermined mold fill profile. For example, one
or more pressure levels over discrete time periods may be achieved
during a mold fill profile according to mold configurations and the
remaining amount of melt in the pressure chamber. Once the mold
fill profile has executed subroutine 142 initiates subroutine 144
to release gas from the pressure chamber and return the melt in the
chamber to the ready level. As illustrated in FIG. 8(f) bubble tube
ready level sensing subroutine 148, as previously described, may be
used to determine when the melt has returned to ready level.
Subroutine 150 holds the melt at the ready level. In addition to
bubble tube sensing, after the mold line machinery moves the
indexed filled mold away from the external end of the dosing tube
and before the next unfilled mold is moved into the indexed
position for fill, laser sensing and/or wire probe sensing may be
used in lieu of bubble tube ready level sensing, or as a supplement
to bubble tube ready level sensing.
[0048] Subroutine 152 determines whether a refill (recharge) of
melt in the pressure chamber is required. Typically this is
predetermined based upon the volume of the cavities in the molds
being filled and the capacity of the pressure chamber. However, in
other examples of the invention, a direct means of sensing the
level of melt in the pressure chamber may be utilized. If a
recharge is not required, subroutine 154 energizes the dosing tube
retract actuator. The dosing tube continues to retract away from
the surface of the indexed mold until subroutine 156 senses that
the dosing tube has fully retracted, when subroutine 158
de-energizes the dosing tube retract actuator. Full retraction of
the dosing tube may be accomplished by the use of a mechanical
limit switch on the external dosing tube assembly. Execution of
subroutine 160 blows a stream of air across the external opening of
the dosing tube to remove any remnant of melt from the mold fill,
and subroutine 162 sends a signal to the mold line machinery that
the indexed mold has been filed. At this point the process returns
to subroutine 133 on FIG. 8(d) to wait for the next empty mold to
be indexed for filing from the furnace.
[0049] If subroutine 152 determines that a recharge of melt in the
pressure chamber is required, as illustrated in FIG. 8(h), while
subroutines 164, 166, 168, 170 and 172 are being executed for
retracting the dosing tube and sending an indexed mold filled
signal to the mold line machinery, subroutine 174 brings the
pressure chamber to atmospheric pressure, for example, by opening
gas exhaust port 43. Then subroutine 176 is executed to energize
the sealing tube open actuator. The sealing element continues to
move away from the sealing port until subroutine 178 senses that
the sealing port opened limit switch has been activated. The
sealing port opened limit switch may be a mechanical limit switch
mounted on the sealing tube assembly external to the pressure
chamber. The sealing port opened limit switch changes state when
the sealing tube element has fully moved to the open position and
the de-energize sealing tube open actuator subroutine 180 is
executed to stop the actuator. Ideally when the sealing port 22 is
opened, melt will flow into the pressure chamber until it reaches a
melt level equal to that in the heating chamber. However, the speed
of the mold line machinery may index an empty mold for filling
before a complete refill of the pressure chamber, and in order to
not delay the rate of mold filling, a less than full recharge of
the pressure furnace may be accomplished. Subroutine 184 determines
whether the recharge of the pressure chamber is complete. The
determination may be based upon the amount of time that the sealing
port is open, or in other examples of the invention, direct sensing
of the melt level in the pressure chamber may be utilized.
Subroutine 184 passes process control to subroutine 102 in FIG.
8(a) when recharge of the pressure chamber has been accomplished,
and the mold filing process continues. In some examples of the
invention, extension and retraction of the dosing tube is not
required if the dosing tube is feeding a fixed launder as further
described below. For these examples of the invention, the
non-limiting example of a process control of the present invention
illustrated in FIG. 8(a) through FIG. 8(h) are suitably modified to
accommodate a fixed dosing tube.
[0050] Alternative examples are contemplated within the scope of
the invention. For example, rather than pressure discharging the
measured melt directly into a mold from furnace 10, the discharge
may be to an intermediate reservoir from which a container is
filled by gravity release of melt from the reservoir. Alternatively
the discharge may be to a launder that gravity feeds the molten
metal into a mold. In some examples of the invention it may not be
necessary to extend and retract the dosing tube. In these examples,
the dosing tube sealing bellows may or may not be used. Further
contemplated within the scope of the invention is the disclosed
features of the pressure chamber in combination with a heating
chamber and/or a receiving chamber of various configurations.
[0051] FIG. 7 diagrammatically illustrates one example of an
integrated arrangement of molten metal supply sources, M.sub.1
through M.sub.n feeding a supply launder distribution network 52a,
that can be optionally connected to a furnace launder distribution
network 52b via one or more metal treatment vessels (MT), or
directly to the furnace launder distribution network. The molten
metal supply sources can be metal melting furnaces, such as
vertical stack scrap and/or ingot aluminum, or other metal charge,
melting furnaces, as known in the art. The metal treatment vessels
provide a means for treating the molten metal output from the
melting furnaces, such as the removal of hydrogen gas, oxides,
impurities and other active metals in the molten metal, as known in
the art. The furnace launder distribution network 52b supplies the
molten metal to a plurality of molten metal pressure pour furnaces
10 of the present invention (designated DF.sub.1 through DF.sub.n
in FIG. 7). Molten metal pressure pour furnaces 10 discharge doses
of the molten metal as described herein. Mold transport machinery
94 is diagrammatically illustrated with exemplar molds 96 being
transported to and from each furnace for sequential indexing in
position (mold 96a) for filling from pressure pour furnace 10. The
launder distribution networks are typically configured as an open
heated trough and can be arranged for gravity flow of the molten
metal from the supply source to the molten metal pressure pour
furnaces.
[0052] The metering valve of the present invention may also be used
to control the flow of a molten metal between any adjoining molten
metal containing components other than the heating chamber and
pressure chamber of a molten metal pressure pour furnace. For
example, FIG. 9(a) illustrates metering valve 64 of the present
invention comprising a sealing port 22 and sealing means, such as
sealing element 30a at one end of sealing tube 30. In this
arrangement of the invention the adjoining molten metal containing
components are launder 52 and pressure chamber 56 of low pressure
molten metal furnace 54. Opening 19 in a wall of the pressure
chamber is generally aligned with the outlet of sealing port 22.
The launder is typically an open channel using gravity flow of
molten metal to the pressure chamber, but may also be an enclosed
component and employ other means for achieving the flow of molten
metal. The launder may be heated (e.g., by electric heating
elements) to keep the molten metal in it at a desired temperature.
In a low pressure melt furnace, the melt is displaced vertically
upwards through supply tube 58 and into the cavities of mold 62,
which is indexed on top of the pressure chamber by mold line
machinery (not shown in the drawing). Melt in the pressure chamber
is forced up the supply tube by injecting a gas at a low pressure
into gas port 60. A low pressure is used so that the mold's
cavities fill slowly upwards to ensure that there is no entrained
air in the die. After one or more molds are filled in this manner,
the melt in the pressure chamber must be replenished. Sealing port
22 of metering valve 64 is opened by removing sealing element 30a
from the sealing port as previously described, after the pressure
chamber has been depressurized. Melt from launder 52 flows through
the sealing port and into pressure chamber 56 through opening 19,
preferably until the level of the melt in the pressure chamber is
at the same level as it is in the launder. This level is
illustrated by molten metal load line 61 in FIG. 9(a) (shown as a
dashed line). Upon recharging pressure chamber 56 with molten
metal, the metering valve is closed by inserting sealing element
30a in the sealing port as previously described above. Since
generally in this example of the invention, metering valve 64 does
not protrude into a pressurized chamber, bellows 29 is an optional
component. Sealing plate 25 in this non-limiting example of the
invention, is shown as a separate element that is attached to a
wall of connecting low pressure chamber 56. In other examples of
the invention, the sealing plate may be incorporated into the
connecting wall of the low pressure chamber, and the cylindrical
end of sealing port 22 of metering valve 74 would open directly
into the interior of the pressure chamber, rather than through
intervening opening 19. FIG. 9(b) diagrammatically illustrates an
integrated arrangement of molten metal supply sources, M.sub.1
through M.sub.n feeding a supply launder distribution network 52a,
that can be optionally connected to a furnace launder distribution
network 52b via one or more metal treatment vessels (MT), or
directly to the furnace launder distribution network. The furnace
launder distribution network 52b supplies the molten metal to a
plurality of low pressure furnaces, LPF.sub.1 through LPF.sub.n.
The flow of molten metal to each low pressure furnace is controlled
by a metering valve 64. Mold transport machinery is
diagrammatically illustrated by dash lines 66. The mold transport
machinery line delivers empty molds to, and receives full molds
from, each low pressure furnace. Mold 62 illustrates a mold indexed
for fill from low pressure furnace LPF.sub.1.
[0053] FIG. 10(a) illustrates an alternative method of controlling
the flow of molten metal to a low pressure furnace. In this method
a double metering valve chamber 68 of the present invention is
used. Double metering valve chamber 68 is connected between launder
70 and pressure chamber 56 of low pressure molten metal furnace 54.
As shown in FIG. 10(a), each of the two metering valves, 74 and 76
in the double metering valve chamber comprise a sealing port 22 in
sealing plate 25, and sealing means, such as sealing element 30a at
one end of sealing tube 30. In this example of the invention, the
two sealing plates form walls of the double metering valve chamber.
Opening 19 in a wall of the pressure chamber is generally aligned
with the outlet of the sealing port for the metering valve adjacent
to the wall. When melt in pressure chamber 56 of molten metal
pressure furnace 54 must be replenished, both metering valves are
opened by removing sealing elements 30a from their respective
sealing ports as previously described, after the pressure chamber
has been depressurized. Molten metal in the double metering valve
chamber and launder 70 flows into pressure chamber 56 through the
two open sealing ports and opening 19 in the pressure chamber's
wall preferably until the level of the melt in the pressure chamber
is at the same level as it is in launder 70 and double metering
valve chamber 68. This level is illustrated by molten metal load
line 71 in FIG. 10(a) (shown as a dashed line). Upon completion of
recharging pressure chamber 56 with molten metal, metering valve 74
is closed by inserting sealing element 30a in its sealing port as
previously described above. Metering valve 76 may alternatively be
closed at the same time as metering valve 74, or may remain open to
allow refilling of the double metering valve chamber, after which
time, metering valve 74 can be closed. Closure of metering valve 76
is accomplished by inserting sealing element 30a in its sealing
port as previously described above. After closure of metering valve
74, one or more molds are filled with melt in the pressure chamber
by injecting a gas into gas port 72 to force molten metal up supply
tube 58 and into the cavities of mold 62 that has been indexed by
mold line transport machinery onto the top of the pressure chamber.
Optionally as shown in FIG. 10(a) a gas pressure equal to the
pressure applied to the melt in the pressure chamber can be applied
to the melt in the double metering valve chamber when both metering
valves 74 and 76 are closed, if required to prevent a back flow of
melt into the double metering valve chamber. If the double metering
valve chamber is not pressurized, bellows 29 is optional for each
metering valve. Sealing plate 25 in this non-limiting example of
the invention for metering valve 74 adjacent to the wall of the
pressure chamber, is shown as a separate element that is attached
to a wall of connecting low pressure chamber 56. In other examples
of the invention, the sealing plate may be incorporated into the
connecting wall of the low pressure chamber, and the cylindrical
end of sealing port 22 of metering valve 74 would open directly
into the interior of the pressure chamber, rather than through
intervening opening 19. FIG. 10(b) diagrammatically illustrates an
integrated arrangement of molten metal supply sources, M.sub.1
through M.sub.n feeding a supply launder distribution network 52a,
that can be optionally connected to a furnace launder distribution
network 52b via one or more metal treatment vessels (MT), or
directly to the furnace launder distribution network. The furnace
launder distribution network 52b supplies the molten metal to a
plurality of low pressure furnaces, LPF.sub.1 through LPF.sub.n.
The flow of molten metal to each low pressure furnace is controlled
by a double metering valve chamber 68. Mold transport machinery is
diagrammatically illustrated in similar fashion as that in FIG.
9(b).
[0054] While each of above examples of the invention utilize a
single sealing port in a sealing plate, the scope of invention
includes providing more than one sealing port in each sealing
plate, with each of the sealing ports having appropriate sealing
means to selectively control the flow of molten metal between the
adjoining molten metal containing components.
[0055] The foregoing examples do not limit the scope of the
disclosed invention. The scope of the disclosed invention is
further set forth in the appended claims.
* * * * *